DESCRIPTION (from the application): This study has been designed to develop an experimental model and provide pilot data that will be used to investigate the relationship between the initial tension applied to an anterior cruciate ligament (ACL) graft at the time of fixation ("initial graft tension") and the healing response of the graft. With the tools, techniques and data provided from this study it will be possible to embark on a long-term investigation that evaluates the interaction between initial graft tension, knee joint kinematics, and the structural/material properties of the ACL graft. Reconstruction of the ACL using autografts or allografts is common following ACL rupture. However, clinical studies indicate that the long-term success of this procedure is variable and that joint arthrosis persists following treatment. Our previous work indicates that one of the primary variables influencing the outcome of an ACL reconstruction procedure is the initial graft tension. Currently, there is little information regarding the relationship between initial graft tension and its effect on the healing response of the graft, and the kinematic behavior of the knee. Animal models of ACL surgery have been popular for evaluating different reconstructive techniques. However, the initial graft tension has not been properly controlled. A clinically relevant way to control initial graft tension is to apply tension to the graft that restores normal anteroposterior (A-P) knee laxity. However, the laxity inherent to the human knee joint is much greater than that of most animals. A method of measuring knee laxity with greater resolution is required. In this study, we will determine if the goat model can be used to evaluate the interaction between initial graft tension and its healing. The specific aims of the study are to develop the tools required to evaluate the effect of initial graft tension on graft healing, to determine baseline data on the interaction between initial graft tension, strain and A-P knee laxity, and to provide pilot data regarding the effect of initial graft tension on knee joint kinematics and the material properties of the graft during healing. The study will be divided into four parts; 1 ) development of an A-P laxity test system and extra-articular graft tensioning device, 2) an in situ evaluation of the relationship between initial graft tension, graft strain, and A-P knee laxity prior to graft fixation, 3) an in situ evaluation of the relationship between resultant graft load after fixation and graft strains, and 4) an in vivo feasibility study designed to test the structural properties of the graft and the change in A-P laxity during healing. These data will be used for future R29 and R01 graft applications. The model will then be expanded to evaluate the initial graft tension on other variables that effect the success of ACL reconstruction; including graft type, graft placement, and rehabilitation.